{
  "eventId": "GRB 260511A",
  "body": "A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin,\nA. Tsvetkova,  M. Ulanov, and T. Cline,\non behalf of the Konus-Wind team, report:\n\nThe long-duration GRB 260511A\n(Fermi-GBM detection: Fermi GBM team, GCN 44529;\nRoberts et al., GCN 44548; \nBALROG localization: Preis & Greiner, GCN 44531;\nSVOM detection: Godet et al., GCN 44532;\nNuSTAR detection: Waratkar et al., GCN 44555) \ntriggered Konus-Wind at T0=22416.401 s UT (06:13:36.401).\n\nThe burst light curve shows a multipeaked structure\nwhich starts at ~T0-4.6 s and has a total duration of ~20.5 s.\nThe emission is seen up to ~6 MeV.\n\nThe Konus-Wind light curve of this GRB is available at\nhttp://www.ioffe.ru/LEA/GRBs/GRB260511_T22416/\n\nAs observed by Konus-Wind, the burst\nhad a fluence of 1.72(-0.05,+0.05)x10^-5 erg/cm2,\nand a 64-ms peak flux, measured from T0+0.482 s,\nof 6.96(-0.71,+0.71)x10^-6 erg/cm2/s\n(both in the 20 keV - 10 MeV energy range).\n\nThe time-averaged spectrum of the burst\n(measured from T0 to T0+16.640 s)\nis best fit in the 20 keV - 10 MeV range\nby a power law with exponential cutoff model:\ndN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)\nwith  alpha = -0.79(-0.08,+0.09)\nand Ep = 187(-8,+8) keV (chi2 = 107/99 dof).\nFitting by a GRB (Band) model yields the same alpha and Ep,\nand an upper limit on the high energy photon index: beta < -3.1\n(chi2 = 107/98 dof).\n\nThe spectrum near the maximum count rate\n(measured from T0+0.256 to T0+8.448 s)\nis best fit in the 20 keV - 10 MeV range\nby a power law with exponential cutoff model:\ndN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)\nwith  alpha = -0.66(-0.08,+0.08)\nand Ep = 187(-6,+7) keV (chi2 = 88/86 dof).\nFitting by a GRB (Band) model yields the same alpha and Ep,\nand an upper limit on the high energy photon index: beta < -2.9\n(chi2 = 87/85 dof).\n\nAll the quoted errors are at the 68% confidence level.\nAll the quoted values are preliminary.\n",
  "subject": "Konus-Wind detection of GRB 260511A",
  "submittedHow": "web",
  "bibcode": "2026GCN.44585....1R",
  "circularId": 44585,
  "submitter": "Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>",
  "createdOn": 1778604902269,
  "format": "text/plain"
}